In certain reduction processes for finely particulate iron ore, for example the FINEX® process, direct reduced iron (DRI) is produced in fluidized-bed reactors by means of a reducing gas. This direct reduced iron has a degree of reduction of about 50-95%, depending on the operational method, and is finely particulate in common with the iron ore used. For complete reduction and to produce pig iron, the direct reduced iron DRI is supplied, after a compacting step in which so-called hot compacted iron (HCI) is obtained, to a storage device or charging device, through which a reducing gas possibly flows, and from there to a smelting unit, for example a melter gasifier. A storage device, also called an HCI bin, or charging device fulfills, inter alia, a buffer function for ensuring that hot compacted iron is charged continuously into the smelting unit. Furthermore, it makes it possible to preheat materials which are additionally to be charged into the smelting unit, for example pellets or lump ore or coke, by the reducing gas. In this case, the storage device is arranged above the smelting unit in order to make charging from the storage device into the smelting unit in the direction of the force of gravity possible.
During normal operation of a FINEX® installation, after the compacting the predominant part of the hot compacted iron obtained in the compacting step is supplied directly in the hot state to the storage device or charging device.
During normal operation of a FINEX® installation, after the compacting another part of the hot compacted iron obtained in the compacting step is utilized in order to provide a reservoir of compacted iron stored outside the storage device or charging device. This reservoir of compacted iron is typically required, for example, during the start-up or shut-down of a FINEX® installation. In conventional systems, the hot compacted iron which is not conveyed directly into the storage device is typically cooled very quickly in a quench tank with water and then stored in the open under atmospheric conditions. As soon as this cooled, stored compacted iron may be required for addition into the smelting unit, it is supplied to the storage device or charging device. It is preheated in the latter before being charged into the smelting unit.
It may be disadvantageous in this case that the compacted iron cooled in quench tanks tends toward reoxidation upon storage, and that a high input of energy is required to preheat said compacted iron before it is charged into the smelting unit. The time required for preheating the material may additionally increase the duration of the start-up process. Furthermore, the operation of the quenching apparatuses is often complex and necessitates time-consuming and expensive handling and disposal of cold briquetted iron and slurry. The installation parts involved may require costly maintenance and operation.
The same conditions also apply of course if, instead of a FINEX® process with HCI as the primary product, use is made of a process in which hot briquetted iron (HBI) is produced as the—briquetted, i.e. compacted—primary product from oxidic iron carriers.
In the case of non-compacted primary products, too, for example low reduced iron (LRI), it is accordingly disadvantageous not to store the primary product in the hot state.